a) Field of the Invention
The invention is directed to an arrangement for recording and reproducing images of an object to be examined having an illumination system, an image-generating recording system, and a controlling and evaluating computer. The arrangement is suitable in particular for measurement systems for spectrometric examination of metabolism and of microcirculation which graphically display spatial or temporal differences in order to determine pathological changes or therapeutic changes in the object to be examined.
Further, the invention is directed to an image-generating method for detecting spatial and/or temporal, medically relevant differences in anatomical structures and functional characteristics of an object to be examined which is illuminated for image generation and selectively stimulated or provoked.
b) Discussion of the Related Art
For significant detection of pathological or therapeutic changes in the course of a disease, different methods for imaging the retina are employed within the framework of ophthalmologic diagnostics above all so that, apart from static information that is spatially resolved at a point in time, dynamic retina characteristic values can be obtained, with or without additional provocation or stimulation, from image sequences. In particular, these are systems for determining spectral temporal or spatial differences and systems for detecting microcirculation values and for functional imaging.
Due to different, uncomparable illumination situations within an image (varying spatial lighting) and between different images, e.g., a change in the main focus of illumination, occurrence of shadows or reflections during spontaneous eye movement, the determination of very slight changes in brightness, position and shape that is required for purposes of detection is subject to a high error rate which sometimes renders measurements useless.
Therefore, in a solution known from DE 38 18 278 C2, the differences in illumination are eliminated by scaling the video signals to the video signal of a reference wavelength. The stated object in DE 38 18 278 C2 is to substantially eliminate methodic and subjective errors in the evaluation and comparison of different images which are recorded at the same time or at different times. For the purpose of directly displaying image changes, the recording beam path is split by beamsplitters into at least two partial beam paths for one and the same image field of the eye, and means for selecting optical information are arranged in at least one partial beam path.
This optical concept is disadvantageous in particular because of the adjustments required for implementing the partial beam paths, the extremely high light stress to which the patient is subjected, and the fact that no simple constructional variants which would simplify the apparatus and reduce costs can be derived from the concept. In addition, the suggested technical solution for functional imaging can be used only conditionally.